Dawson City’s Water and Wastewater Facilities
By Kalpna Solanki CPHI(C) BSc MBA
Visiting Canada’s North
On a recent trip to Whitehorse, I decided to take a bit of a ‘detour’ to the City of Dawson, and the trip was well worth it. Dawson City, with a population of 1,577 (2021 census), is a fascinating northern community at the confluence of the Klondike and Yukon Rivers and boasts a mixture of First Nations heritage and Gold Rush history. The city is marked by Beringia, an Ice Age period which formed its unique landscape, the Tr’ondëk Hwëch’in, who have called this area home for centuries, as well as the Klondike Gold Rush, that put this city on the tongue of stampeders worldwide.
Clockwise – Marc (left), Kalpna (upper left), TC (upper right), Jonathan
(middle right), Michael (right)
Some things you notice about Dawson City are that the roads are not paved within the historic section of the city, retaining the Klondike Gold Rush town ambience. Also, most of the buildings in the historical area have frontier-style building façades, and there are also several well-preserved frontier-style buildings. Dawson City is also part of the Tr’ondëk-Klondike UNESCO World Heritage Site, announced in September 2023. The Klondike Gold Rush in the late 1800s only lasted a few short years, but its legacy and impact on this region and its indigenous people lives on. More than a Century later, gold mining remains an economic mainstay and has produced close to 14 million ounces of gold in the past 120 years. More recently, tourism has become the main economic driver in this gold rush town and in 2023, Dawson City was chosen by Frommer’s Travel Guide as “One of the best places to go” in the World.So, what about water treatment, water distribution, wastewater collection, and wastewater treatment?
My day started off with a meeting with Jonathan Howe, Public Works Manager with the city of Dawson, and I found out that water and wastewater are handled by different groups. Water Treatment, Water Distribution, and Wastewater Collection are overseen by the City of Dawson. However, Wastewater Treatment is overseen by the Government of Yukon.
Water Treatment
The town’s 40-year-old drinking water treatment plant was unable to treat water to meet the Canadian Drinking Water Quality Guidelines. Thus, the Yukon Government started the process to replace Dawson City’s aging water treatment plant with a modern facility. Although the Water Treatment facility is new, consultation with the city’s Heritage Advisory Committee was needed to ensure it fit in with the architecture of the surrounding buildings. The Yukon Government retained Associated Engineering to provide design and construction services for a new water treatment facility. The building façade was designed to replicate an early 1900s cold storage building, reflecting the town’s character and rich history. The design also ensured that local materials and trades could be employed for construction to benefit the local economy.
Distribution System Pumps
The water source is four GUDI wells around 200 metres away from the facility. Being GUDI wells in close proximity to the river, the water quality is heavily influenced by the river. As is unique to other northern cities, Dawson City has a process to prevent water freezing in the lines during the winter. For larger services such as a 20 plex, there are recirculation systems. However, most homes have a bleeder system that allows for bleeding of water at a rate of around 1 L/min. Whilst bleeders keep the water flowing, they also result in increased demand for treated water, increased volume in the wastewater collection system, as well as an increased load for the wastewater treatment facility.
First, the raw water goes through three banks of cartridge filters. The system involves a two-stage filtration system using 5µ and 1µ filters. The 5µ filters are washable and reusable, cleaned every three months, and replaced every 6 months. The filtered water goes through a UV system, and then is treated with chlorine gas. Due to the proximity of the facility to the residential area of the city, there is a chlorine scrubber in place in case there is a leak.
Leaks
The treated water then goes to two reservoirs with a total volume of 5,560 m3 to allow for a contact time of 6 hours. If the system’s distribution pumps cannot keep up with demand, the fire pump kicks in.
In the Winter, water comes in at a temperature of around 2.5°C and goes out at around 5°C. But the heating of the water in the facility during the winter is not enough to keep water flowing through the distribution network when the temperatures drop below freezing, thus the use of bleeders in most of the distribution system.
Boilers to Heat the Water in the Winter
Water from the facility is distributed throughout the city via a water distribution system, but also via Bulk Water Delivery trucks. This well designed and well operated facility will enable Dawson City residents and visitors to enjoy a safe and reliable source of drinking water for many years to come.
EOCP Certified Bulk Water Delivery Operator Filling Up
Wastewater Treatment
For several decades, Dawson City had the ignominious award of being one of Canada’s poorest performers on wastewater treatment. The historic city pumped raw sewage into the nearest major water body. A federal search warrant and raid in 2000 found that tested water, screened only for big ‘lumps’ before hitting the Yukon River, was potentially toxic to fish. The town pleaded guilty to a subsequent Fisheries Act charge, for which the fine was up to $1 million.
At that time, Yukon’s territorial chief justice, Heino Lilles, decided to order the city to build an appropriate wastewater treatment plant rather than paying the fine. Little did he realize that this decision would result in a multi-million-dollar boondoggle, where years later, the discharge from the facility meets the quality parameters but not the volume parameters in the winter months and in the summer meets the quantity parameters, but not the quality parameters.
The complications began around the time of the sentencing, when planners concluded the proposed sewage treatment plant would cost several times the initial estimate. Lilles’s judgment required the facility be completed by September 2004, but he granted the first of many extensions when Dawson said it was back to the drawing board. To confuse matters further, the territorial government removed Dawson’s mayor and council in 2004 after multiple ambitious projects helped tip the city into bankruptcy.
In 2008, planners got the court-ordered deadline for the sewage project completion pushed back once again, to 2011. But then, a month later, residents voted overwhelmingly in a referendum to block the $17-million lagoon from being completed at a site near the entrance to town. So, forced back to square one. With the clock ticking, the Yukon government inked a deal with Vancouver-based Corix Water Systems to build a mechanical treatment plant in town, at an estimated cost of $24.8 million. But deadlines needed to keep being pushed back and costs kept on going up.
The plant was designed and constructed by Corix Water Systems at an estimated cost of $34.3 million. On 7 July 2009, the project broke ground when Dawson City partnered with the Yukon government by signing a Memorandum of Understanding to build the project. Start-up testing of the boiler was undertaken in August 2012 and the plant commenced operations by Corix in 2013 following completion of tests. This wastewater treatment facility is the most unique one I have ever visited, and the challenges borne by the Operators who run the facility are quite significant.
The plant is a mechanical plant located at the lowest part of the city allowing for gravity flow except for a few areas where some lift stations are needed.
There is an influent sump and pumps push the wastewater through various stages of treatment in the plant. There are mechanical and manual screens in parallel in place. However, typically, only the mechanical screens are used, and the manual screens are used only when the mechanical screens are being serviced. Unfortunately, servicing is needed on a regular basis due to the flushing of wipes.
Influent Sump
While I was there, the facility was still in recovery mode from a major process upset due to some local upgrades involving excavation together with a torrential downpour that resulted in large volumes of rocks, gravel, and silt being washed into the system fatally damaging the mechanical screen… and the manual screen needed to be used for almost 8 months.
Exacerbating the problem is that while the mechanical option has a 4mm screen, the manual has a larger aperture bar screen which allows larger objects such as wipes to come through. These are then sometimes found further along in the process in the clarifier and even the aeration tank. When the mechanical screen is offline, wipes need to be removed every other day from the impeller in the aeration tank.
Westside Clarifier
Adding to the woes, there is also a problem with flammable liquids coming into the system. To handle this, there is a Flammable Liquid Diverter and organics are evaporated off.
What makes the City of Dawson’s wastewater treatment plant so unique is its use of an aerobic activated sludge process called Vertreat (vertical treatment), which consists of two 1.4m diameter shafts installed 100m deep in the ground.
One of the Vertreat Chambers
There is an impeller in each tank and the contents are agitated somewhat. The next in the process is a clarifier, then filter disks, and then UV. The solids go through a vertical filter press.
The Full Process
Thus, in addition to not being able to solve some of the critical issues this plant was designed and built for, there are also major challenges related issues such as the 10 filter plates that did not have a process in place for maintenance. These plates weigh around 200 kg when dry, but more than 900 kg when wet. The filter plates need maintenance every two months at the best, and twice weekly the worst times. In addition, the parts are difficult to get, and are expensive costing around $60,000 during the Summer.
Corix continued to operate the plant, under contract, until February 2017 when Dawson Community Services took over operations and maintenance. Originally, the plant was to be operated and maintained by the City of Dawson, but in 2015 it asked the Government of Yukon to manage the plant until it was fully functional and financially sustainable, and the plant continues to be operated by the Government of Yukon.
Currently, it costs the Government of Yukon and City of Dawson approximately $950,000 annually to operate the facility. This cost is significantly higher than anticipated and is higher than any other community in Yukon, including the City of Whitehorse. Keep in mind that this is for a population of fewer than 2,000 people usually with an absolute peak of around 5,000 people in the Summer.
In 2019, the Yukon government realized that maybe it needed to cut its losses and pursue a new wastewater treatment plant option. Now, the plan is to go back to the idea of what works in that climate – a sewage lagoon. But where? To date, agreement on a location has not been achieved, and it is unlikely that the project will be completed by the 2026 target date.